An emotional former North Charleston police officer told a mesmerized South Carolina courtroom Tuesday he feared for his life when he fatally shot an unarmed black man at a traffic stop last year, a tragedy that reignited Black Lives Matter protests across the nation.

The officer, Michael Slager, who is white, testified he pursued Walter Scott on foot after Scott fled the traffic stop. Slager said they scuffled and that Scott wrested away Slager's Taser. Slager said Scott was charging at him when he pulled his gun and fired.

"I saw that Taser coming at me. I knew I was in trouble," a teary Slager said. "I knew I would be overpowered."

Video from the scene shows the Taser on the ground when Slager begins shooting. But Slager, who is charged with murder, said he did not see it that way the day of the tragedy.

The fatal confrontation began when Slager pulled over Scott's 1991 Mercedes for a broken tail light. A bystander's cellphone video, which went viral in the days after the encounter, begins seconds before Slager starts shooting and shows Scott fleeing from Slager, who fires eight shots. Scott, 50, was hit three times in the back, once in the buttocks and once on the ear.

Prosecutor Bruce DuRant pressed Slager on his state of mind, suggesting Slager was angry and not afraid when he shot Scott. Defense lawyer Andy Savage tried to dismiss DuRant's line of questioning, asking Slager if he was in a good mood on April 4, 2015, the day the shooting took place. Slager, 35, said he was upbeat before the shooting because the next day was Easter Sunday and he was scheduled to have three days off.

"After April 4th it's been a roller coaster," he said. "I've been destroyed by this. The Scott family has been destroyed by this. It's horrible."

Slager was fired from the force and charged with murder within days of the release of the cellphone video. If convicted, he could face life in prison.

Slager, who has been free since January on $500,000 bond, said some of his jail time was spent in a cell next to Dylann Roof. Roof is accused of a shooting rampage in June 2015 that killed nine African American worshippers at a historically black Charleston church.

Slager is also awaiting trial in federal court, charged with violating Scott's rights, obstruction of justice and a gun violation. The city of North Charleston agreed to pay a $6.5 million settlement to the Scott family.